The layered Li[Ni1/3Mn1/3Co1/3]O2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni1/3Co1/3Mn1/3]3O4 and lithium hydroxide as raw materials. The physical and el...The layered Li[Ni1/3Mn1/3Co1/3]O2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni1/3Co1/3Mn1/3]3O4 and lithium hydroxide as raw materials. The physical and electrochemical behaviors of Li[Ni1/3Mn1/3Co1/3]O2 were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, field emission scanning electron microscopy （FESEM） and electrochemical charge/discharge cycling tests. The results show that the difference in pretreatment process results in the difference in compound Li[Ni1/3Co1/3Mn1/3]O2 structure, morphology and the electrochemical characteristics. The Li[Ni1/3Mn1/3Co1/3]O2 prepared by solution phase route maintains the uniform spherical morphology of the [Ni1/3Co1/3Mn1/3]3O4, and it exhibits a higher capacity retention and better rate capability than that prepared by ball mill method. The initial discharge capacity of this sample reaches 178 mA-h/g and the capacity retention after 50 cycles is 98.7% at a current density of 20 mA/g. Moreover, it delivers high discharge capacity of 135 mA-h/g at a current density of 1 000 mA/g.展开更多
Using oxalic acid and stoichiometrically mixed solution of NiCl2, CoCl2, and MnCl2 as starting materials, the triple oxalate precursor of nickel, cobalt, and manganese was synthesized by liquid-phase co-precipitation ...Using oxalic acid and stoichiometrically mixed solution of NiCl2, CoCl2, and MnCl2 as starting materials, the triple oxalate precursor of nickel, cobalt, and manganese was synthesized by liquid-phase co-precipitation method. And then the LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion battery were prepared from the precursor and LiOH·H2O by solid-state reaction. The precursor and LiNi1/3Co1/3Mn1/3O2 were characterized by chemical analysis, XRD, EDX, SEM and TG-DTA. The results show that the composition of precursor is Ni1/3Co1/3Mn1/3C2O4·2H2O. The product LiNi1/3Co1/3Mn1/3O2, in which nickel, cobalt and manganese are uniformly distributed, is well crystallized with a-NaFeO2 layered structure. Sintering temperature has a remarkable influence on the electrochemical performance of obtained samples. LiNi1/3Co1/3Mn1/3O2 synthesized at 900 ℃ has the best electrochemical properties. At 0.1C rate, its first specific discharge capacity is 159.7 mA·h/g in the voltage range of 2.75-4.30 V and 196.9 mA·h/g in the voltage range of 2.75-4.50 V; at 2C rate, its specific discharge capacity is 121.8 mA·h/g and still 119.7 mA·h/g after 40 cycles. The capacity retention ratio is 98.27%.展开更多
LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron micr...LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron microscopy (TEM),energy dispersive spectroscopy (EDS),charge-discharge cycling,cyclic voltammetry (CV),and electrochemical impedance spectroscopy (EIS).Uniform coated layer with a thickness of about 3 nm was observed on the surface of LiNi1/3Co1/3Mn1/3O2 particle by TEM.At 0.5C and 2C rates,1.5% (mass fraction) AlF3-coated LiNi1/3Co1/3Mn1/3O2/Li in 2.8-4.3 V versus Li/Li+ after 80 cycles showed less than 3% of capacity fading,while those of the bare one were 16.5% and 45.9%,respectively.At 5C rate,the capacity retention of the coated sample after 50 cycles maintained 91.4% of the initial discharge capacity,while that of the bare one decreased to 52.6%.EIS result showed that a little change of charge transfer resistance of the coated sample resulting from uniform thin AlF3 layer was proposed as the main reason why its rate capability was improved obviously.CV result further indicated a greater reversibility for the electrode processes and better electrochemical performance of AlF3-coated layer.展开更多
Alumina coated LiNi1/3Mn1/3Co1/3O2 particles were obtained by a simple method of solid state reaction at room temperature. The reaction mechanism of solid state reaction at room temperature was investigated. The struc...Alumina coated LiNi1/3Mn1/3Co1/3O2 particles were obtained by a simple method of solid state reaction at room temperature. The reaction mechanism of solid state reaction at room temperature was investigated. The structure and morphology of the coating materials were investigated by XRD, SEM and TEM. The electrochemical performances of uncoated and Al2O3-coated LiNi1/3Co1/3Mn1/3O2 cathode materials were studied within a voltage window of 3.00?4.35 V at current density of 30 mA/g. SEM, TEM and EDS analytical results indicate that the surface of LiNi1/3Mn1/3Co1/3O2 particles is coated with very fine Al2O3 composite, which leads to the improved cycle ability though a slight decrease in the first discharge capacity is observed. It is proposed that surface treatment by solid state reaction at room temperature is a simple and effective method to improve the cycle performance of LiNi1/3Co1/3Mn1/3O2 particles.展开更多
The nano SnO2-modified LiNi1/3Co1/3Mn1/3O2 was successfully prepared by a carrier transfer method. The pristine and modified samples were characterized with various techniques such as XRD, SEM, XPS and EDS. The result...The nano SnO2-modified LiNi1/3Co1/3Mn1/3O2 was successfully prepared by a carrier transfer method. The pristine and modified samples were characterized with various techniques such as XRD, SEM, XPS and EDS. The results showed that the SnO2particles did not enter the crystal structure of LiNi1/3Co1/3Mn1/3O2, many nano SnO2 particles were uniformly covered on the surface of LiNi1/3Co1/3Mn1/3O2 and the modified thin layer could inhibit the dissolution of transition metal oxides. The electrochemical tests indicated that the existence of nano SnO2 could improve the discharge capacity and rate capability owing to the decreased interfacial polarization, The cycling stability was remarkably improved at room temperature and 55 ℃. The XRD patterns of the fresh NCM electrode and after 50 cycles proved that the structural change of NCM was not so effective on the capacity fade.展开更多
采用碳酸盐共沉淀-高温固相法制备了一系列表面碳包覆改性(w=1.0%,2.0%,3.0%)的LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料,借助X射线衍射(XRD)分析、扫描电镜(SEM)、透射电镜(TEM)、电化学阻抗谱(EIS)和恒电流充放电测试等表征手段对材料...采用碳酸盐共沉淀-高温固相法制备了一系列表面碳包覆改性(w=1.0%,2.0%,3.0%)的LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料,借助X射线衍射(XRD)分析、扫描电镜(SEM)、透射电镜(TEM)、电化学阻抗谱(EIS)和恒电流充放电测试等表征手段对材料的晶体结构、微观形貌和电化学性能进行了较系统的研究。结果表明,碳成功地包覆在了材料颗粒的表面,碳包覆改性后的材料具有良好的α-Na Fe O2结构(空间群:R3m),且随着包碳量的增加,一次颗粒平均尺寸逐渐增大(从177 nm增至209 nm)。表面的无定形碳层可以提高材料的电子导电率,减少电极材料与电解液的副反应,故而碳包覆材料的电化学性能都有了一定程度提升。包覆碳量为2.0%的样品高倍率和长循环性能最好,在2.7~4.3 V,1C下循环100次后,容量保持率为93%;在0.1C、0.2C、0.5C、1C、3C、5C、10C和20C时的放电比容量分别为:155、148、145、138、127、116、104和96 m Ah·g-1。在超高倍率50C(9 A·g-1)时,其放电比容量还能达到62 m Ah·g-1(原始LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2材料仅为30 m Ah·g-1),倍率性能十分优异。展开更多
基金Project(20871101)supported by the National Natural Science Foundation of ChinaProject(2009WK2007)supported by Key Project of Science and Technology Department of Hunan Province,ChinaProject(CX2009B133)supported by Colleges and Universities in Hunan Province Plans to Graduate Research and Innovation,China
文摘The layered Li[Ni1/3Mn1/3Co1/3]O2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni1/3Co1/3Mn1/3]3O4 and lithium hydroxide as raw materials. The physical and electrochemical behaviors of Li[Ni1/3Mn1/3Co1/3]O2 were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, field emission scanning electron microscopy （FESEM） and electrochemical charge/discharge cycling tests. The results show that the difference in pretreatment process results in the difference in compound Li[Ni1/3Co1/3Mn1/3]O2 structure, morphology and the electrochemical characteristics. The Li[Ni1/3Mn1/3Co1/3]O2 prepared by solution phase route maintains the uniform spherical morphology of the [Ni1/3Co1/3Mn1/3]3O4, and it exhibits a higher capacity retention and better rate capability than that prepared by ball mill method. The initial discharge capacity of this sample reaches 178 mA-h/g and the capacity retention after 50 cycles is 98.7% at a current density of 20 mA/g. Moreover, it delivers high discharge capacity of 135 mA-h/g at a current density of 1 000 mA/g.
文摘Using oxalic acid and stoichiometrically mixed solution of NiCl2, CoCl2, and MnCl2 as starting materials, the triple oxalate precursor of nickel, cobalt, and manganese was synthesized by liquid-phase co-precipitation method. And then the LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion battery were prepared from the precursor and LiOH·H2O by solid-state reaction. The precursor and LiNi1/3Co1/3Mn1/3O2 were characterized by chemical analysis, XRD, EDX, SEM and TG-DTA. The results show that the composition of precursor is Ni1/3Co1/3Mn1/3C2O4·2H2O. The product LiNi1/3Co1/3Mn1/3O2, in which nickel, cobalt and manganese are uniformly distributed, is well crystallized with a-NaFeO2 layered structure. Sintering temperature has a remarkable influence on the electrochemical performance of obtained samples. LiNi1/3Co1/3Mn1/3O2 synthesized at 900 ℃ has the best electrochemical properties. At 0.1C rate, its first specific discharge capacity is 159.7 mA·h/g in the voltage range of 2.75-4.30 V and 196.9 mA·h/g in the voltage range of 2.75-4.50 V; at 2C rate, its specific discharge capacity is 121.8 mA·h/g and still 119.7 mA·h/g after 40 cycles. The capacity retention ratio is 98.27%.
基金Project(50542004) supported by the National Natural Science Foundation of ChinaProject(1960-71131100017) supported by Graduate Degree Thesis Innovation Foundation of Central South University,China
文摘LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron microscopy (TEM),energy dispersive spectroscopy (EDS),charge-discharge cycling,cyclic voltammetry (CV),and electrochemical impedance spectroscopy (EIS).Uniform coated layer with a thickness of about 3 nm was observed on the surface of LiNi1/3Co1/3Mn1/3O2 particle by TEM.At 0.5C and 2C rates,1.5% (mass fraction) AlF3-coated LiNi1/3Co1/3Mn1/3O2/Li in 2.8-4.3 V versus Li/Li+ after 80 cycles showed less than 3% of capacity fading,while those of the bare one were 16.5% and 45.9%,respectively.At 5C rate,the capacity retention of the coated sample after 50 cycles maintained 91.4% of the initial discharge capacity,while that of the bare one decreased to 52.6%.EIS result showed that a little change of charge transfer resistance of the coated sample resulting from uniform thin AlF3 layer was proposed as the main reason why its rate capability was improved obviously.CV result further indicated a greater reversibility for the electrode processes and better electrochemical performance of AlF3-coated layer.
基金Project(50604018) supported by the National Natural Science Foundation of China
文摘Alumina coated LiNi1/3Mn1/3Co1/3O2 particles were obtained by a simple method of solid state reaction at room temperature. The reaction mechanism of solid state reaction at room temperature was investigated. The structure and morphology of the coating materials were investigated by XRD, SEM and TEM. The electrochemical performances of uncoated and Al2O3-coated LiNi1/3Co1/3Mn1/3O2 cathode materials were studied within a voltage window of 3.00?4.35 V at current density of 30 mA/g. SEM, TEM and EDS analytical results indicate that the surface of LiNi1/3Mn1/3Co1/3O2 particles is coated with very fine Al2O3 composite, which leads to the improved cycle ability though a slight decrease in the first discharge capacity is observed. It is proposed that surface treatment by solid state reaction at room temperature is a simple and effective method to improve the cycle performance of LiNi1/3Co1/3Mn1/3O2 particles.
基金financially supported by National Science Foundation for Fostering Talents in Basic Research of China(No.J2013-002)
文摘The nano SnO2-modified LiNi1/3Co1/3Mn1/3O2 was successfully prepared by a carrier transfer method. The pristine and modified samples were characterized with various techniques such as XRD, SEM, XPS and EDS. The results showed that the SnO2particles did not enter the crystal structure of LiNi1/3Co1/3Mn1/3O2, many nano SnO2 particles were uniformly covered on the surface of LiNi1/3Co1/3Mn1/3O2 and the modified thin layer could inhibit the dissolution of transition metal oxides. The electrochemical tests indicated that the existence of nano SnO2 could improve the discharge capacity and rate capability owing to the decreased interfacial polarization, The cycling stability was remarkably improved at room temperature and 55 ℃. The XRD patterns of the fresh NCM electrode and after 50 cycles proved that the structural change of NCM was not so effective on the capacity fade.
文摘采用碳酸盐共沉淀-高温固相法制备了一系列表面碳包覆改性(w=1.0%,2.0%,3.0%)的LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料,借助X射线衍射(XRD)分析、扫描电镜(SEM)、透射电镜(TEM)、电化学阻抗谱(EIS)和恒电流充放电测试等表征手段对材料的晶体结构、微观形貌和电化学性能进行了较系统的研究。结果表明,碳成功地包覆在了材料颗粒的表面,碳包覆改性后的材料具有良好的α-Na Fe O2结构(空间群:R3m),且随着包碳量的增加,一次颗粒平均尺寸逐渐增大(从177 nm增至209 nm)。表面的无定形碳层可以提高材料的电子导电率,减少电极材料与电解液的副反应,故而碳包覆材料的电化学性能都有了一定程度提升。包覆碳量为2.0%的样品高倍率和长循环性能最好,在2.7~4.3 V,1C下循环100次后,容量保持率为93%;在0.1C、0.2C、0.5C、1C、3C、5C、10C和20C时的放电比容量分别为:155、148、145、138、127、116、104和96 m Ah·g-1。在超高倍率50C(9 A·g-1)时,其放电比容量还能达到62 m Ah·g-1(原始LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2材料仅为30 m Ah·g-1),倍率性能十分优异。
